This amphibian, native to eastern Australia, is famous for its unique mode of reproduction: the females swallow their eggs and raise the tadpoles in their stomachs, eventually giving birth to froglets through their mouths.

Researchers note that during the brooding stage the frogs' stomachs stop producing hydrochloric acid to prevent damaging the tadpoles. This tactic could have been studied by researchers looking for new stomach ulcer treatments; unfortunately, both species of brooding frog are believed to be extinct.